This invention relates to an ink jet apparatus wherein droplets of ink are ejected from an orifice of an ink jet.
U.S patent applications Ser. No. 336,603, filed Jan. 4, 1982, now U.S. Pat. No. 4,459,601, and Ser. No. 576,582, filed Feb. 3, 1984 disclose impulse or demand ink jets capable of operating in a synchronous fill-before-fire mode. When operating in this mode, the ejection of a droplet is first preceded by the filling of the ink jet chamber in response to energization of the transducer and the resulting enlargement of the chamber upon demand. Subsequently, a synchronous period of time thereafter, the transducer is de-energized and the volume of the chamber is allowed to contract to its initial state resulting in the ejection of a droplet from the orifice of the ink jet chamber. In one embodiment described in the aforesaid patent applications, a diaphram is utilized between the transducer and the ink jet chamber and the diaphram retracts along with the transducer upon energization of the transducer.
When utilizing a diaphram, it is particularly important that the diaphram actually retract with the transducer upon energization of the transducer so as to allow filling of the chamber. This may be accomplished by preloading the diaphram so as to take advantage of the memory of the diaphram as shown in U.S. Pat. No. 4,418,355. One method of preloading involves the use of a compliant or visco-elastic material between the diaphram and the foot of the transducer.
As should be understood by those of ordinary skill in the art, it is particularly important to control the dimensions of the ink jet chamber to assure the proper formation and ejection of droplets from the orifice of the chamber. Similarly, it is important to maintain uniformity in the size of a restrictor channel feeding the chamber as well as all other portions of the fluidic path to the ink jet chamber. It is, therefore, important to control the thickness of the compliant material so as not to allow it to alter the dimensions of the fluidic path including the chamber thereby assuring uniformity from channel to channel within the ink jet apparatus.
In this connection, it is particularly important to restrict the flow of compliant material into the annular area between the transducer foot and the structural body supporting the transducer and the feet. It is also important to control the undesirable flow of the compliant material in a way which would force the diaphram into the restrictor channels associated with the chamber. It is also important to control the thickness of the compliant material to assure the proper seal between the various laminated layers of the ink jet apparatus. In this regard, it must be appreciated that the laminated structure is subjected to a compressing force by, for example, the screws which may be utilized to change the various laminated layers in place. Variations in the clamping pressure can result in more or less flow of the elastic material changing the characteristics of the ink jet as a result.